This invention relates generally to a patient movement detection system for a bed and, more particularly, to a load cell mounting assembly that can be retrofitted to an existing bed wherein patient movement can be detected and evaluated while a substantial portion of the patient""s weight is still supported on the patient support device.
In a healthcare setting, it is often necessary to monitor a patient in order to ensure that the patient remains in bed. For example, a patient who is subject to dizziness upon standing up might fall and injure himself if he leaves the bed without help. Consequently, it is desirable that a caretaker be alerted when such a patient attempts to move from the bed so the patient can be helped.
One early technique for automatically detecting patient exit from a bed was characterized by a normally-closed mechanical switch mechanism positioned between the upper surface of the mattress and the patient or between the lower surface of the mattress and the support frame. The switch was configured so that the weight of the patient was sufficient to open the switch and the absence of the patient""s weight allowed the switch to return to its closed position. The switch could be connected in series with a source of power, such as a battery, and with an alarm, such as a buzzer, and would cause the alarm to produce an audible noise when the patient rose from the bed.
Modern patient movement detection systems include a plurality of load cells that support the bed and a detecting arrangement that is responsive to the load cells for detecting movement of the patient from the frame, and thus the bed. The detecting arrangement determines a location of a center of gravity of the patient with respect to the support frame and determines whether the location of the center of gravity is within a predetermined region. One known system of this type is disclosed in U.S. Pat. No. 5,276,432 which issued to Travis on Jan. 4, 1994 (the ""432 patentxe2x80x9d). While known systems of this type have been adequate for their intended purposes, they have not be satisfactory in all respects.
For instance, the load cells and associated transmitting hardware and software of the Travis patent are built into the frames of the bed support device, thereby preventing utilizing of the patient movement detection system with any existing beds. These integrated systems can be expensive and are often cost prohibitive for many health care facilities, which would be faced with replacing existing beds to take advantage of this detection system. Since load cell based center of gravity patient movement detection systems are more reliable than the early switch methods, it is desirable to develop an affordable load cell based system that can be retrofitted onto an existing bed in any health care facility.
This invention is directed to a new and useful patient movement detection system that can be retrofitted to an existing bed. The bed includes a base unit. Two pairs of lift arms are pivotally attached to the base unit. Extending between each pair of lift arms is a torque bar. A frame is secured to the torque bars by a plurality of torque bar mounting brackets. Coupled to each torque bar are a number of load cells. The load cells are electrically connected to a control unit that is configured to receive signals from the load cells and to determine patient information from the load cell signals. When the bed is in its lowest position, the load cells engage the floor and the bed is supported only by the load cells.